deight

class MyElement {
  constructor () {
    this.listeners = {}
    setTimeout(() => this.trigger('loaded'), 3000)
  }
  get (event) {
    return this.listeners[event] || (this.listeners[event] = new Set())
  }
  on (event, listener) {
    this.get(event).add(listener)
  }
  off (event, listener) {
    this.get(event).delete(listener)
  }
  trigger (event, ...args) {
    this.get(event).forEach(listener => listener(...args))
  }
}

const element = new MyElement()

const listener = () => console.log('it is loaded')

element.on('loaded', listener)